This protocol evaluates the use of 6 months of suppressive oral acyclovir therapy in neonates following herpes simplex virus disease involving the central nervous system. This is a double-blind, randomized study. Following 21 days of IV acyclovir, neonates will be randomized to receive suppressive acyclovir therapy or to receive identically flavored placebo for a period of six months. Cutaneous HSV recurrences in either group will be treated with open label oral acyclovir.